Talk:Thyristor

Anything to say about thyristors?

GE called them "SCRs" for Silicon Controlled Rectifiers. --Wtshymanski 15:17, 11 May 2005 (UTC)

Added a paragraph about SCR uses as a "crowbar" in power supplies. --mgolden 16:22, 15 Nov 2005 (UTC)

photothyristors

photothyristors ??? —Preceding unsigned comment added by 62.180.229.222 (talk) 08:37, 27 May 2009 (UTC)

merge

The following discussion is closed. Please do not modify it. Subsequent comments should be made in a new section. A summary of the conclusions reached follows.

The result of this discussion was no consensus,. Daybeers (talk) 21:41, 8 April 2018 (UTC)

---

The thyristor entry asks whether the thyristor entry and the Silicon Controlled Rectifier should be combined. I recommend against this. The thyristor is a broad classification of semiconductor devices, of which the Silicon Controlled Rectifier is but one. Others are listed in the thyristor entry and include Gate Turn-Off Thyristors (GTOs), MOS Controlled Thyristors (MCTs), Static Induction Thryistors (SITh), among others. It would be better to link the thyristor entry to these other entries, but describe each individually.

I agree with the above entry. Thyristors include many different devices. The solution is to expand the thyristor article. I'll offer updates in the coming months. Mak17f 17:16, 1 January 2006 (UTC

yeah keep them seperate

Could we move all the details about SCRs out of the thyristor article, into the silicon-controlled rectifier article, and leave behind a Wikipedia:Summary style summary of SCRs? --68.0.124.33 (talk) 02:19, 19 August 2009 (UTC)

The discussion above is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.

details

Could anyone specify the exact function of the gate in the thyristor? It could be better also if an external website is specified on thyristors. There is no mention of the function of the gate on the SCR page as well.

I added the function in past versions, but for some reason it was removed. :-/ Mak17f 15:35, 21 March 2006 (UTC)

I was pleased to see the cross-coupled transistor circuit appearing there and perhaps it could be mentioned that a pair of transistors will function quite well as a thyristor or even a PUT (programmable unijunction transistor, which is also a thyristor of sorts). I am also puzzled by the apparently complete omission of the SCS, or Silicon Controlled Switch, which simply brings the other base lead out of the package and have terminals therefore designated as "anode gate" and "cathode gate" -- see GE Transistor Manual, around since the Mid-1960s to at least the mid-1970s, though I haven't seen a copy since then. --Rtellason (talk) 06:48, 2 January 2008 (UTC)

Please feel free to be bold and add information about SCS devices. Don't forget to reference the GE Thyristor manual.

Atlant (talk) 13:45, 2 January 2008 (UTC)

Edit

Added the function of the gate terminal in the thyristor.Weltanschaunng 14:45, 29 March 2006 (UTC)

Uploaded the image of the thyristor with its three junctions named as J₁,J₂ and J₃. It is requested that the image be formatted according to the wiki format. It may be replaced with a better image with the three junctions named accordingly.Weltanschaunng 12:46, 3 April 2006 (UTC)

the page has a heading "function" and also "function of the gate terminal". it would be better if they are merged under a single heading.

"function of the gate terminal" is now a sub-heading under "function" DFH 14:53, 6 May 2006 (UTC)

Added the image of the v-i characteristics of thyristor Weltanschaunng 15:31, 13 May 2006 (UTC)

Thanks for all your work!

Atlant 20:27, 13 May 2006 (UTC)

Looking at the image of the v-i characteristics of the thyristor added by Weltanschaunng, I noticed the holding current I_H and the latching current I_L should be swapped of place. I revised M. H. Rashid's “Power electronics: circuits, devices, and applications” to be sure. There is also a web resource available with a correct v-i characteristics image at http://www.eng.uwi.tt/depts/elec/staff/rdefour/ee33d/s4_tchar.html.

--Mmarcos.arg (talk) 14:37, 6 August 2011 (UTC)

Added a remark on the definition of "Thyristor" vs. that of "SCR". Unfortunately, IEC standards are bound by very tight copyrigths so I couldn´t go any further...

Why are technical standards so strongly copyrighted? I've never understood that. They are supposed to be established in order for technicians to use them as widely as possible...

biscay 11:25, 04 Dec 2006 (GMT+1)

I have added an external link [6] to IET magazine for the application to HVDC power transmission. The two other links [4] and [5] for this, which are both to ABB articles, appear to be broken. Unless they reconnect soon would someone like to remove them?

Ambrose H. Field (talk) 14:04, 13 July 2009 (UTC)

SCR?

is an scr apart of thyristor. —The preceding unsigned comment was added by 210.211.225.167 (talk • contribs).

An SCR is one of the most-common types of thyristor. TRIACs and DIACs are two other very-common types.

Atlant 11:45, 26 March 2007 (UTC)

How does positive gate voltage/gate current cause easier breakdown of J2? I am a EE instructor and the statement "If a positive potential V_G is applied at the gate terminal with respect to the cathode, the breakdown of the junction J2 occurs at a lower value of V_AK." is almost identical to the statement used in the curriculum here passed down to me, only we say gate current. I have found that this statement confuses my students as it does not make intuitive sense. Intuitively, a positive voltage on the P material would bring us farther from breakdown. I can explain the operation of an SCR using the two transistor model, which my brighter students understand and the rest are still left in the dark. Can this breakdown model be expanded upon or explained more than this? I have yet to find a satisfactory explanation for this statement. Trashmanal 18:16, 11 May 2007 (UTC)

As a suggestion - Could someone post a table of the states of the thyristor, under "function" or "function of gate terminal"? :Tim2008 11:30, 21 August 2008

Status of article

Why does this page only rate mid-importance in the Electronics Project? I have only a casual interest in electrical engineering, but I see references to these gadgets in vastly many contexts. Don't they deserve "high importance", and a really first-rate article?

Ambrose H. Field 18:07, 6 September 2007 (UTC)

According to the importance scale, high importance would be appropriate only if the thyristor is "well-known to a reader with casual electronic knowledge". I don't think that's the case. Foobaz·o< 18:18, 6 September 2007 (UTC)

All sorts of electronic photographic strobes used to be called "thyristor flashes". I bet lots of people know the term "thyristor" from this application. No mention of photoflashes in the article though. Whogue 07:19, 18 October 2007 (UTC)

joel spira, dimming device for electric lighting

the recent demise of mr spira & my reading about his works led me directly to this page about the thyristor, & yet- curiously- neither he nor his uses of the thyristor (if indeed it's the same device) are mentioned. not being an expert on semiconductor developmental history (I know shockley's name & that's about it!) I'll defer to someone else to deal with this, but it needs dealing with. http://en.wikipedia.org/wiki/Joel_Spira_%28businessman%29

duncanrmi (talk) 21:31, 18 April 2015 (UTC)

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Changes Required

Hello Wikipedians,

I'm definitely not a Wikipedian, so a Wikipedian will have fix the "File:Thyristor I-V diagram.svg" as it incorrectly shows the IL being lower than IH.

Definition: The latching current (IL) of a TRIAC is the minimum value of the load current (current flowing between the cathode and anode) that keeps the device conducting when the gate current (IG) is reduced to zero.

Definition: The holding current (IH) of a TRIAC is the minimum value of the load current (current flowing between the cathode and anode) that keeps the device conducting when the gate current (IG) is zero.

After the IG triggers the thyristor, the current (I) must increase higher than IL before IG can be lowered to zero, otherwise the thyristor will turn off.

If I > IL and IG = 0 so the thyristor is latched on, then if I is reduced so I > IH then the thyristor will still remain latched, else if I is reduced further so I < IH then the thyristor will turn off (i.e., I = 0).

Thus, in the drawing, the IL and IH labels should be swapped, and the VH label should be changed to VL.

Also, the text in the Thyristor page should be changed accordingly.

207.107.66.194 (talk) 21:31, 26 March 2016 (UTC)

References

from a simple datasheet lookup for C106 (http://pdf.datasheetcatalog.com/datasheet2/f/0x25l6410fi895a2ge4fdzlkwipy.pdf) which lists Il=5mA max, Ih=3mA max, the diagram https://en.wikipedia.org/wiki/Thyristor#/media/File:Thyristor_I-V_diagram.svg is incorrect with Il and Ih swapped. I lack the skills to edit the picture and provide a fix. jOERG 08:55, 8 January 2020 (UTC) — Preceding unsigned comment added by Joerg rw (talk • contribs)

Erroneous description in “Function of the Gate Terminal”

Surely: Junction J2 never conducts by avalanche breakdown. In the forward conducting mode conduction across J2 is due to holes that originate in the anode heavily roped p-region and have travelled as minority carries across the lightly doped n-region, and elections that originated in the heavily doped cathode n-region and have travelled across the moderately doped p-region, just as the two transistor model suggests; the n and p layers in the middle of the sandwich are much thicker than a transistor base but they still function by conducting minority carriers. The mathematics modelling of Thyristors in “Introduction to Semiconductor Materials and Devices”, M.S. Tyagi, Wiley 1988 makes it clear that the device does operate as two interconnected transistors. Bethyoung1729 (talk) 11:36, 15 June 2019 (UTC)

Something seems off with the explanation

The introduction section explains that the thyristor can be thought of as two complementary BJTs with the collector of each connected to the base of the other. Something about this explanation just does not sit right.

With the two transistor model wired as shown, supposing the thing is initially "ON" it seems that pulling the gate voltage negative with respect to the cathode will decisively return the whole system to its "OFF" state. The NPN base-collector and base-emitter junctions would be reverse biased and almost immediately halt emitter-base and thus emitter-collector conduction of the PNP element.

But the article almost immediately goes on to say that "the thyristor continues to conduct, irrespective of the gate voltage" which seems wholly inconsistent with the prior explanation of a thyristor as two transistors and this inconsistency does not seem helpful for a reader trying to understand how the latching behaviour of a thyristor actually occurs.

I built some simple circuits up in circuitjs to experiment which I cannot share here because apparently Wikipedia will not let me post any links to falstad.com where the simulator is hosted. But anyway at least insofar as that simulator models these components the thyristor latches very differently from two transistors. I may have to order some real parts to try on the bench.

24.53.240.163 (talk) 21:42, 23 June 2020 (UTC)

Image

The image has a picture of an SCR,not a thyristor. If the two articles were one and the same, this would be fine. But if you have a separate page for SCRs, why put a picture of an SCR and not a thyristor?

It doesn't need to be a device rated for 100 amps like this beast. Any thyristor would do. Throw up a picture of an MCR-100 or something. Show that thyristors need not be gigantic high-powered devices. Better yet, a gallery of thyristors in various packages would work great to this end.

I've also just noticed that the description of the image on the thyristor page describes the component as an SCR in English. But, the Russian description says it's a thyristor.

I'll have to try to look up the part number, or at least what I can see of it, and see which one it is. VoidHalo (talk) 11:36, 16 August 2023 (UTC)

So, I found the part number. It's a 55-367-122. Unfortunately, the only resource I found anywhere that was relevant to it just lumped it in with diacs, alternistors, thyristors, SCRs, etc and doesn't include any data sheet or documentation.

https://www.electrical.com/Products/Semiconductorss-Powerex/55-367-122

In light of these ambiguities and lack of any information about this part, I think the image should be replaced with something more common, with more resources or AT LEAST a datasheet, and that we know for certain to be a thyristor.

As I said in my previous post I think something more typical would be better since it better represents what a thyristor would look like in the real world. Not many people are going to deal with 100 amp rated devices. At least for the main image.

But I also think a gallery showing the wide range of packages thyristors come in (with package names) would be a good idea. VoidHalo (talk) 18:09, 16 August 2023 (UTC)

Going below holding current

The article reads:

• [...] or (b) the current through the device (anode−cathode) becomes less than the holding current specified by the manufacturer.

Should we note that often there is a max value for I_H (hold guaranteed) specified, but not min value (opening is guaranteed)? From a design aspect it is important to go below the min value. IIRC, in cases where both values are given, there were off by a factor of 20 or something. -- Pemu (talk) 12:01, 12 April 2024 (UTC)